An instrument that is used to measure insulation resistance is a Megger. It is also known as meg-ohm-meter. It is used in several areas like multi-meters, transformers, electrical wiring, Etc. Megger device is used since the 1920s for testing various electrical devices which can measure greater than 1000meg-ohms.
It is measured using an instrument named Megger test capable of impressing D.C. voltage between its two probes, automatically calculating and then displaying the IR value. Megger test being so popular that “Insulation Resistance” and “Megger Test” are synonymously used.
What is a Megger used for?
The Megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. For good insulation, the resistance usually reads in the megohm range.
What is the minimum acceptable value of insulation resistance?
Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.
What is a good reading when Megging a motor?
Place one meter lead on the ground terminal or wire and place the other meter lead on one of the phase wires or terminals. Press TEST on the meghometer. A very high resistance reading (generally greater than 10 megaohms) will indicate the motor insulation is good.Feb 25, 2021
What is a bad insulation resistance reading?
The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality, ...
What is Megger resistance?
Definition: The Megger is the instrument uses for measuring the resistance of the insulation. If the resistance of the insulation is high, the pointer of the moving coil deflects towards the infinity, and if it is low, then the pointer indicates zero resistance. ...
What is the insulation resistance?
An insulation resistance (IR) test measures the total resistance between any two points separated by electrical insulation. The test, therefore, determines how effective the dielectric (insulation) is in resisting the flow of electrical current.
What do Megger readings mean?
If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes. Any reading above 1.25 is considered excellent.
What does a megohmmeter tell you?
Megohmmeters provide a quick and easy way to determine the condition of the insulation on wire, generators, and motor windings. A megohmmeter is an electric meter that measures very high resistance values by sending a high voltage signal into the object being tested.